#include <iostream>
#include <string>
#include <string.h>
#include <stdlib.h>

using namespace std;

#ifdef _WIN32
#include <windows.h>

string GbkToUtf8(const char *src_str)
{
    int len = MultiByteToWideChar(CP_ACP, 0, src_str, -1, NULL, 0);
    wchar_t *wstr = new wchar_t[len + 1];
    memset(wstr, 0, len + 1);
    MultiByteToWideChar(CP_ACP, 0, src_str, -1, wstr, len);
    len = WideCharToMultiByte(CP_UTF8, 0, wstr, -1, NULL, 0, NULL, NULL);
    char *str = new char[len + 1];
    memset(str, 0, len + 1);
    WideCharToMultiByte(CP_UTF8, 0, wstr, -1, str, len, NULL, NULL);
    string strTemp = str;
    if (wstr)
        delete[] wstr;
    if (str)
        delete[] str;
    return strTemp;
}

string Utf8ToGbk(const char *src_str)
{
    int len = MultiByteToWideChar(CP_UTF8, 0, src_str, -1, NULL, 0);
    wchar_t *wszGBK = new wchar_t[len + 1];
    memset(wszGBK, 0, len * 2 + 2);
    MultiByteToWideChar(CP_UTF8, 0, src_str, -1, wszGBK, len);
    len = WideCharToMultiByte(CP_ACP, 0, wszGBK, -1, NULL, 0, NULL, NULL);
    char *szGBK = new char[len + 1];
    memset(szGBK, 0, len + 1);
    WideCharToMultiByte(CP_ACP, 0, wszGBK, -1, szGBK, len, NULL, NULL);
    string strTemp(szGBK);
    if (wszGBK)
        delete[] wszGBK;
    if (szGBK)
        delete[] szGBK;
    return strTemp;
}
#else
#include <iconv.h>

int GbkToUtf8(char *str_str, size_t src_len, char *dst_str, size_t dst_len)
{
    iconv_t cd;
    char **pin = &str_str;
    char **pout = &dst_str;

    cd = iconv_open("utf8", "gbk");
    if (cd == 0)
        return -1;
    memset(dst_str, 0, dst_len);
    if (iconv(cd, pin, &src_len, pout, &dst_len) == -1)
        return -1;
    iconv_close(cd);
    *pout = '\0';

    return 0;
}

int Utf8ToGbk(char *src_str, size_t src_len, char *dst_str, size_t dst_len)
{
    iconv_t cd;
    char **pin = &src_str;
    char **pout = &dst_str;

    cd = iconv_open("gbk", "utf8");
    if (cd == 0)
        return -1;
    memset(dst_str, 0, dst_len);
    if (iconv(cd, pin, &src_len, pout, &dst_len) == -1)
        return -1;
    iconv_close(cd);
    *pout = '\0';

    return 0;
}

#endif

int main(void)
{
    char *src_str = "葡萄美酒夜光杯";
    cout << "origin string: " << src_str << endl;

#ifdef _WIN32
    // windows default is gbk
    string dst_str = GbkToUtf8(src_str);
    cout << "gbk to utf8: " << dst_str << endl;

    string str_utf8 = Utf8ToGbk(dst_str.c_str());
    cout << "utf8 to gbk: " << str_utf8 << endl;
#else
    // unix default is utf8
    char dst_gbk[1024] = {0};
    Utf8ToGbk(src_str, strlen(src_str), dst_gbk, sizeof(dst_gbk));
    cout << "utf8 to gbk: " << dst_gbk << endl;

    char dst_utf8[1024] = {0};
    GbkToUtf8(dst_gbk, strlen(dst_gbk), dst_utf8, sizeof(dst_utf8));
    cout << "gbk to utf8: " << dst_utf8 << endl;
#endif

    return 0;
}
